It depends on the Sim couples, and what I want for the couple.
I make a lot of family based Sims, so they tend to roll wanting 6 kids at least, with those families I tend to give them more than 6, not all at once, but over time.
Other Sims it varies, I tend to give them the minimum of 3, and may give them more.
If the Sim is based on a preexisting character, for example the Weasleys from Harry Potter, I give them all of their kids, and have to rely on Ginny being born in-game, they always tend to end up with more than their canon kids to get Ginny.
